Procedure

     LX4DEC (Scan for signed integer)

     SUBROUTINE LX4DEC ( STRING, FIRST, LAST, NCHAR )

Abstract

     Scan a string from a specified starting position for the
     end of a decimal number.

Required_Reading

     None.

Keywords

     PARSING

Declarations

     IMPLICIT NONE

     CHARACTER*(*)         STRING
     INTEGER               FIRST
     INTEGER               LAST
     INTEGER               NCHAR

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     STRING     I   any character string
     FIRST      I   first character to scan from in STRING
     LAST       O   last character that is part of a decimal number
     NCHAR      O   number of characters in the decimal number.

Detailed_Input

     STRING   is any character string.

     FIRST    is the location in the string to beginning scanning
              for a decimal number. It is assumed that the
              decimal number begins at FIRST.

Detailed_Output

     LAST     is the last character at or after FIRST such that
              the substring STRING(FIRST:LAST) is a decimal
              number. If there is no such substring, LAST
              will be returned with the value FIRST-1.

     NCHAR    is the number of characters in the decimal number
              that begins at FIRST and ends at last. If there
              is no such string NCHAR will be given the value 0.

Parameters

     None.

Exceptions

     Error free.

     1)  If FIRST is beyond either end of the string, then LAST will be
         returned with the value FIRST-1 and NCHAR will be returned
         with the value 0.

     2)  If STRING(FIRST:FIRST) is not part of a decimal number then
         LAST will be returned with the value FIRST-1 and NCHAR will be
         returned with the value 0.

Files

     None.

Particulars

     This routine allows you to scan forward in a string to locate
     a decimal number that begins on the input character FIRST. Note
     that all signed integers are included in the list of decimal
     numbers. See LX4SGN for a description of signed integers.

     We let S stand for a signed integer and U stand for
     an unsigned integer. With this notation, the strings
     recognized as decimal numbers are:

        U
        S
        S.
        S.U
         .U
        -.U
        +.U

Examples

     Suppose you believe that a string has the form

        X%Y%Z

     where X, Y, and Z are decimal numbers of some unknown
     length and % stands for some non-digit character. You could
     use this routine to locate the decimal numbers in the
     string as shown below. We'll keep track of the beginning and
     ending of the decimal numbers in the integer arrays B and E.

     FIRST = 1
     I     = 0

     DO WHILE ( FIRST .LT. LEN(STRING) )

        CALL LX4DEC ( STRING, FIRST, LAST, NCHAR )

        IF ( NCHAR .GT. 0 ) THEN

           I     = I    + 1
           B(I)  = FIRST
           E(I)  = LAST
           FIRST = LAST + 2

        ELSE

           FIRST = FIRST + 1

        END IF

     END DO

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.2.0, 04-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

        Fixed return value for LAST in $Exceptions section entry #1.

    SPICELIB Version 1.1.0, 28-NOV-1995 (WLT)

        Upgraded the routine to handle strings of the form
        '+.01' and '-.01' which were regarded as non-decimal
        strings before.

    SPICELIB Version 1.0.0, 12-JUL-1994 (WLT)